The Anubias genus is popular among aquarium hobbyists for its robust nature and tolerance for low-light conditions. Despite this hardiness, owners frequently observe leaves turning yellow, a condition known as chlorosis. This discoloration indicates a disruption in the leaf’s ability to produce chlorophyll, signaling an underlying issue with the plant’s environment or care. Understanding the specific cause, from anatomical errors to chemical imbalances, is the first step toward restoring the plant’s deep green color and ensuring long-term health.
When the Rhizome is Buried
The most frequent cause of yellowing specific to this genus relates directly to its unique anatomy. The Anubias plant possesses a thick, horizontal stem known as a rhizome, from which both the leaves and roots sprout. This structure is not designed to be submerged within a dense substrate like gravel or sand. When the rhizome is buried, it becomes deprived of oxygen and is susceptible to rot and necrosis.
This prevents the stem from effectively transporting water and nutrients to the leaves. The ensuing lack of chlorophyll production quickly manifests as widespread chlorosis, often before physical rot is visible. The roots are meant to secure the plant, but the rhizome must be exposed to the oxygenated water column to function correctly.
Signs of Specific Nutrient Deficiencies
If the rhizome is correctly positioned, the yellowing likely points to a lack of essential macronutrients or micronutrients in the water column. A deficiency in Nitrogen (N) presents as uniform chlorosis across the older, lower leaves first. Because Nitrogen is highly mobile within the plant, the Anubias reallocates the limited supply from mature leaves to support newer growth, leaving the older foliage pale.
Conversely, a lack of Iron (Fe) is diagnosed by observing interveinal chlorosis on the newest leaves. Iron is immobile, meaning the plant cannot move it from old tissue to new growth. The newly developing leaves struggle to form chlorophyll, appearing yellow while the leaf veins remain distinctly green.
Magnesium (Mg) deficiency also targets older leaves, but the pattern is distinct from Nitrogen. Magnesium is a central component of the chlorophyll molecule. When lacking, the yellowing starts along the outer edges of the leaf and progresses inward, often leaving a green pattern near the center vein. Identifying where the chlorosis begins—old versus new growth—is the most reliable way to pinpoint the chemical imbalance.
Addressing Light Intensity and Algae
While Anubias is known as a low-light species, improper illumination can still trigger stress or chlorosis. Exposing the plant to overly intense light for prolonged periods can cause photobleaching or stress, which directly inhibits photosynthetic efficiency. The plant’s slow growth rate makes it particularly susceptible to this type of environmental damage.
However, the more common light-related issue is the growth of epiphytic algae on the leaf surface. When light duration or intensity is too high, it encourages the proliferation of tough green spot or brush algae, which coats the slow-growing Anubias leaves. This algal layer acts as a physical barrier, blocking the light from reaching the underlying chloroplasts. The resulting light starvation suffocates the leaf’s ability to produce chlorophyll, leading to gradual yellowing and tissue death. Reducing the duration of the photoperiod often helps curb the algal growth.
Immediate Steps to Revive Your Plant
The approach to reviving a yellowing Anubias depends entirely on the diagnosis, beginning with a physical check of the rhizome. If it was buried, gently uproot the plant and attach the rhizome above the substrate line to driftwood or rock using fishing line or aquarium-safe super glue. This ensures proper water flow and oxygenation around the stem tissue, allowing it to heal and resume function.
Simultaneously, trim off any leaves that are completely yellow or show signs of heavy damage. Removing this senescent foliage redirects the plant’s energy toward producing healthy new growth. Use clean, sharp scissors and cut the leaf stem close to the rhizome to minimize stress.
To resolve nutrient deficiencies, liquid fertilizers should be dosed into the water column, targeting the specific elements identified (N, Fe, or Mg). For long-term feeding, root tabs can be placed in the substrate, but they must be positioned a few inches away from the rhizome to ensure the roots, not the stem, absorb the nutrients. Finally, gently wiping algae from the leaves with a soft cloth will immediately restore the plant’s ability to capture light and resume photosynthesis.